In the course of manufacture of a photoreceptor drum of an organic photoconductor type that is to be used as a photoreceptor in an electrophotographic apparatus, a photosensitive coating solution is coated on a cylindrical drum base body of the photoreceptor. When the cylindrical drum base body is coated, it is necessary that slide hoppers and the like are positioned at predetermined locations around the cylindrical drum and that the clearance between the cylindrical drum and each slide hopper in the radial direction on a sectional circle of the cylindrical drum is adjusted to be constant. In this case, the deviation of the cylindrical drum by only 0.1 mm in the radial direction can cause a great difference in the thickness of a coated layer because a coated layer is extremely thin in its necessary thickness.
It is generally known that such difference in thickness of a coated layer causes various kinds of troubles such as a change of a charged amount in the radial direction of the cylindrical drum, unevenness of sensitivity and a change of residual potential. Therefore, it is very important to position the cylindrical drum accurately.
Heretofore, as drum-positioning methods of this kind, there is known a method wherein a drum is fed continuously through coating heads being touched by position-regulating rollers provided around the drum. Alternatively, a drum is fed continuously through coating heads being touched by a group of plural driving rollers provided in the transport direction. At the same time, the relation in terms of location between an external peripheral surface of the drum and the coating head is adjusted while the coating head is moved horizontally through rollers. These methods are similar to those disclosed in Japanese Patent Publication Open to Public Inspection Nos. 60-50537 and 60-95546 (hereinafter referred to as Japanese Patent O.P.I. Publication].
In all of the conventional apparatuses, however, positioning is conducted with position-regulating rollers or with a group of driving rollers all of them contacting directly a drum. Therefore, the drum is scratched, which is a disadvantage. It is generally known that the scratch on the drum causes electrophotographic characteristics to be worsened.
On the other hand, in the apparatus disclosed in the latter publication, it is essential that the position of a drum is regulated and the position of each coating head is adjusted, but when the coating head is made to be slidable, the coating head tends to be deviated against the drum, and it is particularly difficult to keep the drum and the coating head coaxial.